Important Extra Questions on Probability

A coin is tossed. If it shows head, we draw a ball from a bag consisting of 2 red and 3 black balls. If it shows tail, coin is tossed again. [Answer: {HR1, HR2, HB1, HB2, HB3, TH, TT}]

Two balls are drawn at random in succession without replacement from a box containing 1 red and 3 identical white balls. [Answer: {RW, WR, WW}]

A coin is tossed n times. Find the number of element in its sample space. [Answer: 2^n]

One number is chosen at random from the numbers 1 to 21. What is the probability that it is prime? [Answer: 8/21]

What is the probability that a given two-digit number is divisible by 15? [Answer: 1/15]

Questions for Practice

A game has 18 triangular block out of which 8 are blue and rest are red, and 19 square blocks out of which 7 are blue and rest are yellow. On piece is lost. Find the probability that it was a square of blue colour. [Answer: 1/4]

In a leap year find the probability of

(i) 53 Mondays and 53 Tuesdays

(ii) 53 Mondays and 53 Wednesday

(iii) 53 Mondays or 53 Tuesdays. [Answer: (i) 1/7, (ii) 0, (iii) 3/7]

In a non-leap year, find the probability of

(i) 53 Mondays and 53 Tuesdays.

(ii) 53 Mondays or 53 Tuesdays. [Answer: (i) 0, (ii) 2/7]

Two card are drawn at random from a deck of 52 playing cards. Find the probability of drawing two kings. [Answer: 1/221]

Find the probability that in a random arrangement of the letters of the word UNIVERSITY two I’s come together. [Answer: 1/5]

Try These

Out of 8 points in a plane 5 are collinear. Find the probability that 3 points selected at random form a triangle. [Answer: 23/28]

Find the probability of at most two tails or at least two heads in a toss of three coins. [Answer: 7/8]